The present invention relates to fuel cells and particularly molten carbonate fuel cells. More specifically, the present invention relates to separators for separating adjacent cells in a stack of fuel cells in a molten carbonate fuel cell power plant.
One type of molten carbonate fuel cell comprises an anode electrode spaced apart from a cathode electrode by an electrolyte-retaining matrix. Each electrode is disposed in a reaction region of the cell which is separated from adjacent cells by a separator plate. A corrugated support occupies the space between each electrode and the adjacent separator plate. The corrugations on the two supports are disposed at right angles to each other and respectively permit passage of two different reactant gases in perpendicular directions through the two reactive areas. The passages of one of the supports extend between gas manifolds on opposite sides of the stack of cells for one of the reactant gases, while the passages of the other support extend between gas manifolds on the other to sides of the stack for the other reactant gas.
Each separator plate carries along the opposite side edges thereof two solid metal sealing rails which extend parallel to the support passages and the associated reactive area and toward one end of the stacks of cells, these rails being approximately the same height as the electrode and its support in the associated reactive area of the cell. Similar rails are formed along the other side edges of the separator plate and project toward the other end of the stack of cells or sealing a reactive area of an adjacent cell. Thus, each cell is bounded by two separator plates, the seal rails on one separator plate sealing one of the cell's active areas and the seal rails on the other separator plate sealing the other of the cells' active areas.
The disadvantage of the solid sealing rails is that they cannot adjust to changes in the thickness of the electrodes and the electrode supports. These changes in thickness may result from manufacturing tolerances in the several parts of the cell or from characteristics exhibited by the cell parts in response to operation of the cell. Thus, for example, when the stack of cells is heated, the electrodes and supports undergo thermal expansion, increasing the compressive forces thereon. Over time, the parts of the cell undergo creep which tends to lessen the compressive forces and may cause parts to pull away from the sealing rails and impair the sealing of the active cell areas. Electrical and thermal conductivity between cell components and between adjacent cells may also be impaired.